GB607124A - Process for the manufacture of crystallized glucose of very high purity - Google Patents

Abstract

In a continuous process for crystallizing glucose monohydrate only a fraction of the partially crystallized mass is withdrawn from the crystallizer, and is replaced by an equal volume of solution to be crystallized, preferably by a solution of purity not greater than 86 per cent, the process being characterised by the mass in the crystallizer being kept permanently between 20 DEG and 30 DEG C. The added solution, preferably heated above 80 DEG C., melts small and irregular crystals and the large crystals, after one washing approach 100 per cent purity. The crystal size may be increased by withdrawing a portion of one mass from one crystallizer, heating to 70 DEG C. and returning it to the crystallizer. Crystals of different types may be obtained in one cycle by adding more solution to the crystallizer than that withdrawn for centrifuging, (which yields a small quantity of crystals of very high purity), and feeding a second crystallizer with an amount equal to the excess added to the first, to yield a larger quantity of crystals which are smaller, but still capable of being centrifuged. In examples: (1) a solution of 86 per cent reducing sugars is concentrated to 40 DEG C. Boum<\>ae, under vacuum at 70 DEG C. in an evaporator, is further heated to 75 DEG C. and passed to a crystallizer kept at 25 DEG C. About 10 per cent of the volume in the crystallizer is drawn-off daily to a centrifuge and replaced immediately by fresh juice at 75 DEG C., from the evaporator. The crystals are dried, sifted and bagged, and the mother liquor is mixed with a glucose syrup, concentrated, and casked or made into slabs; (2) 80 per cent of the juice introduced daily to the crystallizer is cooled to 40 per cent before introduction, the remainder being heated to 85 DEG C. The third of the quantity added is centrifuged after crystallization to yield crystals of 100 per cent purity, and the other two thirds are passed to a second crystallizer from which an equal quantity is passed each day to a centrifuge to yield crystals of 99.5 per cent purity. The mother liquors are treated as in (1). (3) glucose juice of 86 per cent purity is heated to 80 DEG C. and fed to a crystallizer maintained at 25-30 DEG C. A quantity equal to one-third of the daily feed is withdrawn from the crystallizer and centrifuged to give crystals of 100 per cent purity, a quantity equal to the remaining two-thirds of the daily feed being passed to, and divided between, two other crystallizers from which an equal amount is withdrawn and centrifuged to give crystals of 99.6 per cent purity. The mother liquors from the first centrifuge are heated to 60 DEG C. and introduced into the second two crystallizers (the amount withdrawn for centrifuging being correspondingly increased) while the mother liquors from the second centrifuge are mixed with syrup or molasses and casked to give an eating syrup. To obtain a mass of large crystals in the crystallizer in starting the process, 10 per cent of the cooled mass is daily drawn-off, heated to 80-90 per cent and returned immediately to the crystallizer. Juice of 90-92 per cent purity may be used for the crystallization process to give a higher crystal yield, but the mother liquors have then not such a good taste as when juice of a lower purity is used.